I wouldn't care if I were you, and there's a good reason for this: the DistrictHeating object is a hot water element anyways.

To be a little more helpful, here's what I would do. I would model the system AFTER the main heat exchanger, which is where is the property line is in many cases:the utility is responsible for the heat exchanger, since a failure can affect their global distribution system, and the property is responsible for whatever is after.

You can calculate the "Nominal Capacity" (W) of the heat exchanger and use that in the DistrictHeating (or let it autosized).

In the end you'll get a DistrictHeating Energy in Joules, which you can always convert back to pounds of steam at 180°C/24 bar if that's what you need.

Edit:

Don't model the heat exchanger at all. Just model the building loop with the district heating object on the supply side, and your VAV terminals on the demand side. Use a setpointmanager that will match your proposed building loop operation: for example it could be an outdoor air reset and the steam flow is throttled to maintain 80°C water outlet temperature when it's really cold outside, and 60°C water when it's mild outside.

If you need to have separate loops (2 heatings loops for 2 different part of the building, and 1 DHW loop for example) you can always do two things:

• Model 3 different loops, each served by a different district heating object (in the end, all it's cares about is energy delivered). This is the easiest.
• Or you can model one master plant loop with the district heating object on the supply side, and 3 HX on the demand side. Control this loop to have a constant temperature. I'm actually wondering if you couldn't set that loop to be at 180°C or if EnergyPlus will be unhappy about it even if you set the PlantLoop maximum temperature to 200C (if you try it, let me know). After all, water in liquid form can be heated to 374°C (provided you can pressurize it at ton)